New Zealand Agricultural Fieldays founding member Russ Rimmington said wet days were "bloody great" because exhibitors got genuine buyers.

"Over the years as an exhibitor and in the administration side, we have found that the wet days - hand on heart - to be fantastic. That's when the good sales are done."

Poor weather might mean lower attendance because tyre kickers stayed home, but he knew exhibitors that had achieved some of their best sale figures on that kind of day. Rimmington hasn't missed a Fieldays for 47 years.

"It affects our [Fieldays] bottom line more than the exhibitors. If we're 10,000 down in people, that's worth about $250,000 to us, but those people that don't go because it's raining aren't going to buy a lot of product anyway."

But fine weather is forecast for Friday - traditionally the biggest day at Fieldays.

Hamilton accommodation is packed and some corporates booked for the next year before they left, moteliers said. They also tended to hit the restaurants at night to meet with clients or unwind.

And steaks were expected to be a top seller by Hamilton's two main hospitality groups. Macklow said around 250kg of steak would be sold at the Phoenix Group's Smith & McKenzie Chophouse during Fieldays.

"[Fieldays] equates to our largest week of the year, turnover-wise across the group so we're just looking forward to getting into it."

Some of the group's restaurants might see a 60 to 70 per cent increase, he said.

Fieldays communications executive Vicki Annison said about 900 exhibitors were spread across 1300 sites this year - and those were booked out from December. The largest exhibitor for 2014 was thought to be Palmerston North C B Norwood Distributors Ltd, which had 11 sites under separate brands.

Visitors were also expected from 37 countries, including Ecuador, Malaysia and Canada.